For the maintenance, and also for the division of cells, it is necessary for the cell to reproduce its genome (DNA), then to transcribe the genes (DNA) into various RNAs among which are messenger RNAs, which in turn direct the synthesis of proteins. The biological medium that permits this is extremely complex. Various enzymes are present in the biological system to carry out these and other cellular functions.
Conditions leading to a pathological situation may result from alterations or degradations of elements in one or another of these steps. Endogenous or exogenous factors can affect the events of these various steps. Conversely, pathological states may be ameliorated by introducing into the biological system suitable entities that act directly or indirectly (but always in a selective fashion) on DNA, RNA and/or enzymes.